If the computer will boot from USB you can install amigo on USB and use syslinux to make the stick bootable.
Or you can use a boot floppy.
BUT, the stock kernel doesn't have USb mass storage hard-compiles, so you need to build an initrd that will load the usb drivers, or re-compile the kernel.
RUNT linux is built on the same thing as Amigo and they have a boot disk that loads USB drivers. You can use that to boot amigo.
The upcoming AmigoXP does this very easily -in fact you can have it installed on USB and hard drive at the same time. When you want to run from USB just plug it in and it gets picked up first. Otherwise the bootloader finds the hard disk installation and boots that. Great way to 'sync' a mobile distro.